Years of working out and eating low

Hi everyone! I’m 24F and I’m completely fed up with my body right now. I’m currently 170 and working out (lifting + 15-20 mins cardio) plus at least 15k steps a day. I have been in this routine for so long now, at least 2 years. When I was 18 I went to a dietitian and went on a very very low diet of 1000 calories when I was at my highest weight of 180. I ended up getting down to 138 in a year. Once I got to that point I stopped following that and increased my calories a little. However, I never went back to eating how I used to eat. Ever since then, I have always eaten around 1200-1500 calories a day plus exercise. I do have a diagnosed eating disorder that I was just recently diagnosed with. I am now at the point where I don’t know what to do. As a result of my ED, I saw another dietitian who told me I need to eat a little more and a bit more frequently. So I did for about 1.5 months, and now I am at 170 which is 5 pounds more than I was then. Additionally, my clothes are tight and I want to throw up when I look in the mirror. I want to stop eating completely but I know I can’t. I feel like no matter how heavy I lift I see no muscle gain, and I know it’s because I don’t eat enough to gain. But I’m mortified of increasing my calories more. If you’re in the same situation or have been through this please help!